The present invention relates to a mixture of surfactants which may be anionic or nonionic and a low molecular weight polypropylene glycol which, when placed in an acidic solution, give a homogeneous solution which, maintains its homogeneity over a wide range of temperature. Another advantage which has been discovered is that in the case of nonionic surfactants, low foam characteristics are observed. The present invention further relates to surface active agents for use in high operating temperatures and high agitation applications. The present invention further relates to the use of such surfactant blends in metal finishing, electroplating, electrolytic metal deposition, acidic cleaning, especially spray applications and rinse aids for automatic dish cleaning compositions.
The present invention further relates to the incorporation of such surfactant blends for use in any application wherein it is desired to have high cloud point and to maintain low foaming.
2. Description of the Related Art
Feighner, U.S. Pat. No. 3,539,518, discloses a low foam nonionic surfactant composition which consists of lower C.sub.1 -C.sub.8 straight chain acyl group capped alcohol ethoxylates. The Patent, at column 3, is addressed to the fact that higher cloud points are indicative of greater water solubility and are desirable in certain applications. Although Feighner et al disclose high cloud point surfactants of a general formula which could be derived through reactions from surfactants of the present invention, Feighner et al are not concerned with the same family of nonionic surfactants as the present invention. Further, Feighner et al do not disclose the use of these surfactants with a low weight polypropylene glycol as a surfactant blend and in acidic medium.
Decker et al, U.S. Pat. No. 4,410,447 disclose a liquid low foaming nonionic surfactant which has good wetting characteristics and good scouring and detergency properties. The surfactant comprises a block-random structure represented by the formula: EQU R--O--A.sub.x --B--H
wherein R is a primary alkyl group having from 7-11 carbon atoms, A is oxypropylene, x is an integer from 2-15 with the proviso that the sum of the number of carbon atoms in the alkyl group and x is from 12 to about 22, B is a random mixture of oxyethylene oxypropylene groups with molar ratio of oxyethylene to oxypropylene in the mixture being such that the total ratio of oxyethylene to oxypropylene in A and B is from 0.2:1 to 1.5:2 while the molar ratio of oxyethylene to oxypropylene in the random mixture is 1:1 and preferably from 2:1 to 5:1. The R--O is defined as the residue of the alcohol employed in the condensation reaction with hydrogen. The surfactants disclosed in Decker et al have a cloud point ranging from 20.degree. to 60.degree. C. There is no showing in Decker et al of the high cloud points of the present invention nor of the use of nonionic surfactants with a low weight polypropylene glycol in an acidic medium to render surfactant blends which have low foaming characteristics and high cloud points and are useful in the applications as previously noted herein.
Fong et al, U.S. Pat. No. 4,592,809 disclose nonionic surfactants prepared by the reaction of ethoxylated bis-phenols and sulfating agents. These surfactants are useful in metal electroplating baths and processes to increase the useful operating temperature limits of the bath in comparison to those using other surfactants. A high cloud point is desired in the medium and it is necessary that this surfactant be capable of serving its intended purpose and not otherwise affecting the bath plating or deposition characteristics of the electroplating bath. Fong e al differ from the present invention because Fong et al achieve these characteristics by use of a sulfating agent, whereas the present invention achieves this result using polypropylene glycol.
Boehmer, U.S. Pat. No. 3,890,238 discloses liquid polyoxyalkylene polymers which demonstrate an increased cloud point which may be raised by the addition to the solution of an alkali metal salt of an organic thiol acid having at least one --SH group. The present invention is not concerned with the addition of alkali metal salts of organic thiol acids having at least one --SH group to raise the cloud point. Rather, the present invention is directed to the use of certain nonionic surfactants and anionic surfactants with a low weight polypropylene glycol in an acidic medium to produce a low foam, high cloud point surfactant blend.
None of the art, insofar as is known, discloses an aqueous mixture of a nonionic surfactant or an anionic surfactant with a low molecular polypropylene glycol in an acidic medium.
The block copolymers useful in the present invention may be a polyoxyethylene/polyoxypropylene type surfactant or, may be of the polyoxypropylene/polyoxyethylene nonionic surfactants. What is also unexpected in the present invention, is that certain anionic surfactants may be used in an acidic medium together with a low molecular weight polypropylene glycol to produce a high cloud point surfactant blend. It was previously known in the art that an anionic surfactant in an acidic medium would oil out of solution.
It has been discovered that certain anionic surfactants which contain at least some ethylene glycol hydrophilicity, when blended with a low molecular weight polypropylene glycol, produce a clear surfactant blend in acidic medium which has a very high cloud point. These anionic surfactants have the general formula: EQU R--O(C.sub.2 H.sub.4 O).sub.n --SO.sub.3 X
wherein R is a hydrocarbon chain, an aromatic ring, a combination of a hydrocarbon chain and an aromatic ring, and mixtures thereof, containing 7 to 15 carbon atoms, and n is a number from 2 to 14, and X is a hydrogen atom or alkali metal such as sodium or potassium.